JSFiddle - React, Tailwind, and code Playground

HTML

<p>
This is some text with a 
footnote.<sup><a href="#section1">[1]</a></sup>
Next sentence.
</p>
<br><br><br><br>
<p id="section1">
[1] The footnote itself.
</p>

CSS

sup {
  vertical-align: super;
  font-size: smaller;
}